Kato H, Fujisawa H, Minagawa T
Virology. 1986 Aug;153(1):80-6. doi: 10.1016/0042-6822(86)90009-7.
A tail fiber of phage T3 is a trimer of the product of gene 17 (gp17). Treatment of T3 phage particles with chymotrypsin resulted in cleavage of only the tail fiber protein, at a site near the distal end of the fiber, causing a decrease of about 10% in the size of gp17 in the treated virion. The N-terminal amino acid sequences of intact and cleaved tail fiber proteins were identical and corresponded to that deduced from the nucleotide sequence of gene 17 except for the absence of the initiation Met residue. These results indicate that cleavage of the tail fiber occurred near the C terminus and suggest that gp17 polypeptides are oriented parallel to each other in the tail fiber. Association of tail fibers with the tail involves the N-terminal region of gp17. Under mild conditions of SDS-polyacrylamide gel electrophoresis, intact tail fibers dissociated from virions but cleaved ones did not. The nucleotide sequences indicate that T3 and T7 gp17 contain many sites that are potentially sensitive to chymotrypsin. In fact, free tail fibers, purified from T3-infected cells, were cleaved to many smaller fragments by chymotrypsin. These results suggest that the attachment of the tail fibers to the tail may induce a change(s) in the configuration and/or arrangement of gp17 to mask the sensitive sites from cleavage by chymotrypsin.
噬菌体T3的尾丝是基因17产物（gp17）的三聚体。用胰凝乳蛋白酶处理T3噬菌体颗粒，结果仅在尾丝蛋白靠近远端的位点处发生切割，导致经处理的病毒体中gp17的大小减少约10%。完整和切割后的尾丝蛋白的N端氨基酸序列相同，除了起始甲硫氨酸残基缺失外，与从基因17的核苷酸序列推导的序列一致。这些结果表明尾丝的切割发生在C端附近，并提示gp17多肽在尾丝中彼此平行排列。尾丝与尾部的结合涉及gp17的N端区域。在SDS-聚丙烯酰胺凝胶电泳的温和条件下，完整的尾丝从病毒体上解离，但切割后的尾丝则不然。核苷酸序列表明T3和T7的gp17含有许多潜在的对胰凝乳蛋白酶敏感的位点。事实上，从感染T3的细胞中纯化的游离尾丝被胰凝乳蛋白酶切割成许多较小的片段。这些结果表明，尾丝与尾部的附着可能会诱导gp17的构象和/或排列发生变化，从而掩盖被胰凝乳蛋白酶切割的敏感位点。
